Can top and method of making same



Dec. 31, 1968 E. c. FRAzE 3,418,956

CAN TO1 2 AND METHOD OF MAKING SAME Original Filed Feb. 4, 1965 United States Patent O 3,418,956 CAN TOP AND METHOD OF MAKING SAME Ermal C. Fraze, 355 W. Stroop Road, Dayton, Ohio 45429 Original application Feb. 4, 1965, Ser. No. 430,253, now

Patent No. 3,303,960, dated Feb. 14, 1967. Divided and this application Oct. 18, 1966, Ser. No. 641,064

6 Claims. (Cl. 113-116) This application is Ia division of S.N. 430,253, filed Feb. 4, 1965, and now Patent No. 3,303,960, issued Feb. 14, 1967.

This invention relates to a can to hold a beverage wherein the can top is formed with a tear strip that is manually removable to form an opening through which the beverage can may be emptied. The liquid content may be `poured through the opening into a glass, but frequently a purchaser drinks the beverage directly from the opening that is formed by removal of the tear strip. One problem to which the invention is directed is to prevent injury to the drinkers lips or tongue by the edges of such a can opening.

Even if the can top is made of relatively soft sheet metal such as an aluminum alloy, the tearing of the metal by the removal of the tear strip may leave a rough edge that is hazardous to some degree. If the metal is tincoated steel, however, the severance of `the tear strip invariably leaves a hazardous sharp jagged edge. One expedient that has been heretofore suggested to remedy this situation is to form outwardly embossed ribs in the can top along the opposite sides of the opening to space vthe drinkers lips away from the can top. The ribs, however, are necessarily shallow and do not afford adequate protection from a saw tooth edge that is formed by ripping a tear strip from a sheet steel can top.

The present invention makes a new approach to this problem by offsetting the can top rearwardly in the region of the tear strip to `form an elongated radially positioned recess with the tear strip at the bottom of the recess. When the removal of the tear strip leaves a hazardous edge, the hazardous edge is spaced substantially inwardly from the plane of the can top and the can top itself serves as an effective guard for the drinkers tongue and lips.

The application of this concept to the construction of a metal can top involves a problem in that it is more dithcult to initiate severance of a tear strip that lies in the bottom of a recess than a tear strip in the plane of the can top. A feature of the invention is that this difficulty is avoided by forming an elongated recess in the can top with the recess extending radially from a central region of the can top. With this arrangement the leading end of the tear strip may be at least near the plane of the can top in the central region of the can top to make it easy to initiate severance of the tear strip while the `remaining radially outward position of the tear strip is offset substantially inwardly from the can top. Thus when the tear strip is removed to form an opening in the can top, the torn metal edge of the opening is offset inwardly from the top in the outer radial region that is contacted by the drinkers lips.

Another further feature of the invention is the concept of further reducing the hazard to the drinker by forming the recess with walls that are curved inwardly to overhang the torn metal edges of the can opening. Another difficulty arises here because the overhanging Walls make the overhung regions inaccessible for scoring of the metal by conventional tooling. The invention teaches that this difhculty may be avoided by first forming the recess with a nonplanar bottom wall, then scoring the nonplanar bottom wall to form the tear strip and finally, flattening the bottom wall to expand the bottom wall in all directions.

In the preferred practice of the invention the bottom wall of the recess is formed with an outwardly extending longitudinal bulge, the bulge providing a groove that follows the margin of the bottom wall. The metal is scored along the bottom of the groove and then the bottom wall is attened to remove the bulge. The consequent spreading of the bottom wall in both la-teral directions spreads apart the score lines on opposite sides of the recess and at the same time converts the side walls of the recess to the desired overhanging configuration. In addition the flattening of the bulge elongates the bottom wall to displace the scoring along the radially outer end of the recess to cause the end wall of the recess to overhang the scoring.

In the preferred practice of the invention the overhanging side walls of the recess not only serve to guard the drinkers lips from the rough metal edge of the opening but also have a safety yfunction in guarding against abrupt fluid pressure actuated severance of the tear strip. It has been found that if a can confines a fiuid under pressure, such as a highly carbonated beverage, initial severance of the leading end of a tear strip may trigger instant severance of the remainder of the tear strip in an explosive manner that may project the tear strip several feet at high velocity. This hazard is reduced in the present construction by making the gap between the overhanging walls, i.e. the exit from the recess, narrower than the width of the recess so that the overhanging walls serve as an effective stop against propulsion of the tear strip through the gap.

With the tear strip wider than the clearance between the overhanging side walls to provide this safety feature, the further problem arises of how -to sever and remove the tear strip without interference by the overhanging Walls. This further problem is solved by scoring one side of the tear strip appreciably deeper than the other side. The deeper scoring reduces the resistance to severance to such an extent that one side edge of the tear strip peels away from the can top faster than the other side edge so that the tear strip progressively turns sidewise to pass between the overhanging side walls as the tear strip is progressively severed.

In a can of the general type to which the invention pertains, wherein a tab is attached to the tear strip by a hollow rivet that is formed in the material of the tear strip, the degree to which the tab and rivet extend above the plane of the can top necessarily increases the axial dimension of the cylindrical Wall of the can since the rim or chime of the can top must extend above all structure on the can top. Consequently providing the usual tear strip and tab `makes it necessary to increase the width of the metal sheet that is rolled to form the can body and the increased width represents in itself a substantial increase in the cost of the can.

A feature of the invention in this respect is that offsetting the tear strip inwardly from the plane of the can top by forming a recess in the can top in effect retracts the hollow rivet that is formed in the tear strip. The invention takes advantage of this fact by further forming an adjoining recess in the can top to receive the tab that engages the rivet. Thus the rinvention in effect retracts both the hollow rivet and the tab. The extent to which a tab and the associated rivet projects outward is determined not only by the extent to which the tab and rivet protrude from the can tap, but also by the degree to which the can top is bulged outwardly.

The outward bulge of the can top is caused in part by the spreading of the metal by the usual scoring operation and in part by the pressure of the conned uid. Fortuitously the offsetting of the metal of the can top to form the recess for the tear strip and the adjoining recess for the tab counteracts both of these causes since the recesses take up metal to compensate for the spreading of the metal and additionally make the can top stronger and more rigid to reduce the extent to which the can top is bulged by interval fluid pressure. In fact the provision of the recesses make it possible to reduce the thickness of the sheet metal stock that is used for the can top.

The features and advantages of the invention may be understood from the following detailed description together with the accompanying drawing.

In the drawing, which is to be regarded as merely illustrative:

FIG. 1 is a plan view of a sheet metal can top at an early stage in its fabrication where the metal of the can top has been offset to form a recess of an initial configuration to accommodate both the tear strip and the tab attached to the tear strip;

FIG. 2 is a cross section along the line 2 2 of FIG. 1 showing the initial configuration of the recess;

FIG. 3 is a fragmentary section along the line 3-3 of FIG. 2 in the region of the hollow rivet by means of which the tab is to be attached to the tear strip;

FIGS. 4, 5 and 6 are similar sections along the lines 4 4, 5-5 and 6-6 respectively of FIG. 2 indicating the initial cross-sectional configuration of the recess;

FIG. 7 -is a fragmentary sectional View showing how an upper die may be advanced against a lower die to flatten the bottom wall of the recess and thus convert the recess from its initial configuration to its final configuration, the conversion resulting in the side walls of the recess overhanging the scoring at the bottom of the recess;

FIG. 8 is a plan view of the finished can top;

FIG. 9 is a greatly enlarged fragmentary transverse sectional view taken along the line 9-9 of FIG. 8 and showing how the scoring is deeper on one side of the tear strip than on the other side of the tear strip;

FIG. 10 is a section of the finished can top taken along the line 10-10 of FIG. S and showing how the recess in the can top reduces the extent to which the tab and the hollow rivet protrude beyond the plan of the surrounding sheet material of the can top; and

FIG. 1l is a transverse section along the line 11-11 of FIG. l0 showing how the tab nests in the recess to reduce the extent to which the tab protrudes beyond the surrounding sheet material.

FIG. l, illustrating an early stage in the fabrication procedure, shows a can top, generally designated 10, of tin-coated sheet steel intended for use in a beverage can, the can top being formed with the usual peripheral flange 11 in preparation for the usual operation of joining the can top to the cylindrical can body. FIG. 1 shows the can top after the sheet material of the can top has been offset inwardly to retract inwardly the tear strip and the tab as well as the hollow rivet in the tear strip by means of which the tab is attached to the tear strip. The result of offsetting the sheet material inwardly is to form a single elongated recess but the recess may be regarded as comprising two recesses that adjoin each other in communication with each other, namely a first recess 12 in the area that will be used for a tear strip and a second recess 15 in the area that is to be occupied by the tab that Iis attached to the tear strip. The first recess 12 is formed with a nonplanar bottom wall and the nonplanar bottom wall is scored along the line 16 to form the desired tear strip 17. In this particular practice of the invention the bottom wall of the first recess 12 is made nonplanar by forming the bottom wall with an upward longitudinal bulge 18. The recess -12 may be of any suitable configuration but in this instance is generally triangular in plan with the apex of the triangle in the central region of the can top and with the base of the triangle at the radial outward end of the recess.

In this initial configuration of the recess 12 as shown in FIGS. 5 and 6, the recess has two steeply sloped side Walls 20 that converge towards the apex of the triangle and the recess has a steeply sloping end wall 22 as the base end of the triangle. The recess 12 is tapered in depth with the bottom wall 24 of the recess inclined gradually upward toward the plane of the can top, i.e., toward the plane of the surrounding sheet material at the radially inner end of the recess. The bulge 18 is also of triangular conguration in plan to form a groove 25 that surrounds the bulge on three sides, the groove being relatively deep across the outer radial end of the recess and gradually decreasing in depth towards the inner end of the recess.

In accord with the teaching of the invention, the continuous line of scoring 16 follows the triangular configuration of the bottom of the groove 25 to form a generally triangular tear strip 17. The leading end of the tear strip 17 where severance of the tear strip is to be initiated is at the apex of the triangle and it is apparent that the described construction makes it easy to initiate the severance of the tear strip both because the leading end of the tear strip is relatively narrow and because the leading end of the tear strip is relatively close to the plane of the can top instead of being at the opposite deep end of the recess 12. It is to be further noted, as shown in FIG. 4, that the extent to which the sheet material is transversly bowed to form the bulge 18 progressively decreases towards the radial inward end of the recess.

FIihe next step in the fabrication procedure is to flatten to a desirable degree the nonplanar bottom wall of the triangular recess by means of a. pair of dies shown in full lines in FIG. 7. The pair of dies comprises a lower die 32 with a planar u-pper working face 34 and an upper die 35 with a planar bottom working face 36. FIG. 5 shows the upper die in phantom poised for the flattening operation and FIG. 7 shows the two dies at the end of the flattening operation. As may be seen by comparing FIGS. 5 and 7, the operation of flattening the bottom wall of the recess 12 t-o convert the recess from its initial configuration to its final configuration results in spreading apart the two portions of the line of scoring 16 that lie on opposite sides of the triangular recess. In addition, the flattening operation spreads the bottom wall of the recess 12 radially to shift outwardly the score line across the radially outward end of the recess. A second consequence of the flattening operation is that the increase in width of the bottom wall displaces the material of Uhe two side walls 20 to change each side wall to an overhanging S- shaped cross-sectional configuration and the increase in the length of the bottom wall changes the wall at the radially outward end of the recess into a configuration to overhang the scoring. Thus each of the side walls 20 forms a smoothly curved lip 38 (FIG. 7) which overhangs the line of scoring 16 as may be seen in FIG. 7, and in addition the end wall of the recess 12 is changed to a similar ovenhanging configuration.

The second recess 15 that seats the tab is of uniform depth and is shown in FIGS. 2 and 4. The uniform depth of the recess 15 may be substantially the depth of the shallow radially inner end of the recess 12.

The final step in the fabrication procedure is to attach a suitable tab to the leading end of the tear strip 17 to serve as a handle for manual severance of the tear strip. Such a tab may be made of any suitable material, may be of any suitable configuration. In this particular embodiment of the invention, as shown in FIGS. 8 and 10, a tab 40 of tin-coated steel is employed that is of substantially the same configuration in plan as the second recess 15 in which it seats. The tab 40 may be permanently attached to the leading end of the tear strip 17 in any suitable manner, for example by spot welding, but in this instance is attached by a hollow rivet 42 that is formed in the tear strip.

In this particular embodiment of the invention the tab is divided into two portions, namely a minor end portion 44 which is attached to the tear strip 17 by the hollow rivet 42 and a major portion in the form of a second class lever 45. The metal of the tab bends freely at the juncture lof the end portion 44 and the lever 45 so that the lever 45 is, in effect hingedly connected to the end portion. The end portion 44 of the tab has an aperture therein through which the hollow rivet 42 extends, the hollow rivet being formed in the material of the tear strip 17. FIGS. 2 and 3 show the initial configuration of the hollow rivet 42 before it is inserted into the aperture of the tab and FIG. 4 shows the hollow rivet 46 in its final configuration at which it engages the rim of the aperture in the tab. Fig. 4 further shows how, in the preferred practice of the invention, the end portion 44 of the tab is anged around the aperture to form a hub 4S that snugly embraces and reinforces the rivet.

T he material of the tab is formed with two slits S by virtue of which the lever 45 is of forked construction, being formed with a pair of fulcrum ends 54 that straddle the hollow rivet 42. The sheet material of the lever 45 is offset and rolled as indicated in FIGS. 8 and ll to form a U-shaped stiffening rib 55 and to form a folded peripheral edge 56. The free end of the lever is preferably slightly bent upward as shown in FIGS. 10 and ll to facilitate manual gripping of the lever. When the lever 45 is swung upward by its free end out of the recess 15, the two fulcrum ends 54 press against the sheet material of the can top on opposite sides of the hollow rivet 42 to provide a highly effective leverage action for tilting the hollow rivet to the extent of initiating severance of the tear strip. With the leading end of the tear strip torn free, the lever 45 is employed as a handle to pull away the remainder of the tear strip.

Since the side walls of the recess 12 overhang the line of scoring 16 in the recess, the gap between the two side walls is less than the width of the tear strip 17 so that the overhanging side Walls tend to keep the tear strip captive in the event that the tear strip is abruptly severed by fluid pressure. In the preferred practice of the invention, one side of the tear strip is scored deeped than the other side to cause the one side to tear easily and to cause the tearing action lon the one side to lead the tearing action on t-he other side. Thus FIG. 9 shows how the line of scoring 16 may be relatively deep on one side of the tear strip 17 to leave an exceptionally thin residual web 58, the scoring along the line 16 of the other side of the tear strip being shallower to leave a thicker residual web 60.

When the tear strip 17 is severed progressively by means of the tab 40 the fact that the tearing action on one side of the tear strip leads the tearing action on t-he other side of the tear strip causes the tear strip to turn sidewise as it is severed. At the sidewise orientation the tear strip passes freely between the overhanging walls of the recess 12 and it is to be noted that the walls are smoothly curved to minimize the possibility of interference with the severance of the tear strip.

When the user severs the tear strip by means of the tab 40 and drinks the beverage directly from the can, the rough edge of metal produced by severance of the tear strip is not a hazard for two reasons. In the rst place, in the region where the users lips and tongue make contact with the container, the rough edge of metal of the can opening is displaced substantially inward from the plane of the can top. The users lips do not extend to the radially inward end of the recess 12 where the edge of the can opening lies close to the plane of the can top. In the second place, the smooth rounded lips along the rim of the recess formed by the opposite side walls as well as the end wall of the recess overhang the rough edges of the can opening and thus serve as a guard to keep the users lips and tongue `out of alignment with the edges of t-he can opening.

My description in specific detail of the selected embodiment of the invention will suggest various changes, substitutions and other departures from my disclosure within the spirit and scope of the appended claims.

I claim:

1. A method of fabricating an easy opening container of sheet material wherein the sheet material is scored to define a tear strip for manual re-moval to form an opening through which the container may be emptied, characterized by the steps of:

offsetting the sheet material of the container to form a recess of an initial conguration with a nonplanar bottom wall in the region where the opening is desired;

scoring the nonplanar bottom wall of the recess to form the tear strip with lines of the scoring extending along the margins of the bottom of the recess; and

flattening the nonplanar bottom wall of the/ recess to expand the 'bottom wall `of the recess in width to spread said lines of scoring apart and thus cause the walls of the recess to be changed in configuration to overhang the lines of scoring.

2. A method as set forth in claim 1 in which the bottom wall of the recess at the initial configuration of the recess is formed with a longitudinal bulge to make the Ibottom wall nonplanar.

3. A method as set forth in claim 1 in which the bottom wall of the recess slopes upward to substantially the plane of the outer surface of the container at one end of the recess with the leading end of the tear strip also extending up the slope of the bottom wall to facilitate initiation of severance of the tear strip.

4. A method as set forth in claim 3 in which the recess is formed in the top end wall of the container and is oriented radially of the end wall; and

in which the recess is of generally triangular configuration with the wider end of the triangle at the radially outward end of the recess.

5. A method of fabricating an easy opening cylindrical container of sheet material wherein the sheet material of the top end of the container is scored to Kdefine a tear strip for manual removal to form an opening through which the user may drink the contents of the container, characterized by the steps of `offsetting the sheet material of the top end of the container to form an elongated recess of an initial configuration positioned radially of the end wall, with the recess formed with a nonplanar bottom wall and with the bottom wall of the recess sloping upward to the plane of the can end at the radially inward end of the recess;

scoring the nonplanar bottom wall of the recess to form a tear strip with the leading end of the tear strip extending up the slope of the bottom wall to substantially the plane of the container end and with lines of the scoring extending along the margins of the bottom wall of the recess;

flattening the nonplanar bottom wall of the recess to expand the bottom wall of the recess to spread said lines of scorin-g apart; and

-attaching a tab to the leading edge of the tear strip to facilitate severance of the tear strip.

6. A method as set forth in claim 3 in which the nonplanar bottom Wall of the initial configuration of the recess has a longitudinal central bulge forming a groove around the bulge; and

in which said lines of scoring are at the bottom of the groove prior to the attening operation.

CHARLES W. LANHAM, Primary Examiner. R. D. GREFE, Assistant Examiner.

U.S. Cl. X.R. ll3-l20, 121 

5. A METHOD OF FABRICATING AN EASY OPENING CYLINDRICAL CONTAINER OF SHEET MATERIAL WHEREIN THE SHEET MATERIAL OF THE TOP END OF THE CONTAINER IS SCORED TO DEFINE A TEAR STRIP FOR MANUAL REMOVAL TO FORM AN OPENING THROUGH WHICH THE USER MAY DRINK THE CONTENTS OF THE CONTAINER, CHARACTERIZED BY THE STEPS OF: OFFSETTING THE SHEET MATERIAL OF THE TOP END OF THE CONTAINER TO FORM AN ELONGATED RECESS OF AN INITIAL CONFIGURATION POSITIONED RADIALLY OF THE END WALL, WITH THE RECESS FORMED WITH A NONPLANAR BOTTOM WALL AND WITH THE BOTTOM WALL OF THE RECESS SLOPING UPWARD TO THE PLANE OF THE CAN END AT THE RADIALLY INWARD END OF THE RECESS; SCORING THE NONPLANAR BOTTOM WALL OF THE RECESS TO FORM A TEAR STRIP WITH THE LEADING END OF THE TEAR STRIP EXTENDING UP THE SLOPE OF THE BOTTOM WALL TO SUBSTANTIALLY THE PLANE OF THE CONTAINER END AND WITH LINES OF THE SCORING EXTENDING ALONG THE MARGINS OF THE BOTTOM WALL OF THE RECESS; FLATTENING THE NONPLANAR BOTTOM WALL OF THE RECESS TO EXPAND THE BOTTOM WALL OF THE RECESS TO SPREAD SAID LINES OF SCORING APART; AND ATTACHING A TAB TO THE LEADING EDGE OF THE TEAR STRIP TO FACILITATE SEVERANCE OF THE TEAR STRIP. 